Construction and operation of vertical shaft furnaces



Oct. 6, 1953 F. P. SOMOGYI ,5 I

CONSTRUCTION AND OPERATION OF VERTICAL SHAFT FURNACES Filed NOV. 16,1949 Patented Oct. 6, 1953 UNITED STATES ATENT OFFICE CONSTRUCTION ANDOPERATION OF VERTICAL SHAFT FURNACES Francis Paul Somogyi, London,England 6 Claims.

This invention relates to improvements in or relating to theconstruction and operation of Vertical shaft furnaces of the kind inwhich discrete material consisting of or containing a solid fuel ischarged from the top and passes down the shaft in countercurrent to anascending air blast introduced into the bottom, and is finally removedfrom the bottom of the shaft. As the material passes down the shaft itstemperature progressively increases until the material reaches a pointat which combustion commences. This point represents the boundarybetween the heating zone and the combustion zone. As the material passesdown through the combustion zone its temperature first rises and thenfalls until the material reaches a second point at which combustionceases. Thereafter the material progressively cools until it reaches thebottom of the shaft. The second point represents the boundary betweenthe combustion zone and the cooling zone.

Since heat is lost from the shaft by radiation in a radial direction,the temperature of any given horizontal cross-section of the material ishigher at the centre of the shaft than at the circumference. As aresult, the depth of the combustion zone is considerably greater at thecentre of the shaft than at the circumference.

It is the main object of the present invention to avoid this difficulty;other objects and improvethe kind specified, wherein a part of theascende ing air blast introduced into the bottom of the shaft is removedat one or more levels from the periphery of the cooling zone, so that apart only of the air blast proceeds onwards up through the combustionzone.

According to this invention also, there is provided a vertical shaftfurnace of the kind specified, having means for introducing an ascendingair blast into the bottom of the shaft, an outlet or outlets forcombustion gases at the topof the shaft, and one or more peripherallydisposed outlets at one or more levels, for a part of the blast air fromthe periphery of the cooling zone of the s aft.

By means of the invention it is possible toin- 2 ing zone reduces thetendency of the combustion zone to extend further down the shaft at thecentre than at the circumference, and thus renders the combustion zonemore nearly uniform in depth.

The invention may be applied with advantage to cement-making. Since thematerial, in this case burnt clinker is now discharged from the bottomof the kiln at a lower temperature than Was previously usual, lesstimeelapses after its discharge before it has cooled sufficiently to befurther handled, and this saving of time is of advantage. Moreover sincethe depth of the combustion zone is more nearly uniform, the conditionsexperienced by the material passing down the shaft vary less with theradial distance of the material from the centre of the shaft than waspreviously the case and therefore a more nearly uniform product results.The quicker cooling also improves the quality of the product by freezingin of the calcium silicate.

The blast air removed from the periphery of the cooling zone is at arelatively high temperature, and may be used for one or more of a numberof purposes. For example in thecase of cement-making, the blast air fromthe cooling zone may be passed to a drying device in which it is used topre-dry nodules or briquettes of cement-forming material before thelatter is charged into the kiln.

By controlling the input of blast air into the bottom of the shaft, andthe escape of blast air from the cooling zone, the lower boundary of thecombustion zone may be adjusted upwards and downwards as desired.

The blast air removed from the cooling zone may be returned wholly or inpart into the combustion zone through peripheral inlets, and theproportion of blast air removed from the cooling Zone and theproportionof blast airreturned t'o the combustion zone may be. regulatedand controlled so as to adjust the lower boundary, of the combustionzone upwards and downwards. A proportion of the blast air removed fromthe cooling zone may also, if desired, be returned through peripherallydisposed inlets into the heating zone whereby heat from the blast airmay be re-introduced into the system.

Control may be effected by a relay mechanism actuated by temperatureresponsive devices, such as thermo-couples, disposed in the furnace wallat different heights and different sides of the furnace, and thearrangements may be such that the lower boundary of the combustion zoneis rotary grate is mounted on a shaft :5 which is connected to drivingmeans not shown. The upper part of the chute 4 is provided with an inlet6 through which an air blast is introduced into the bottom of the shaft2.

A feeding hopper 1 having a chute 8 is disposed vertically above thetop-of the shaft 2 and enclosed in a housing 9 having a chimney Ill forthe outlet of combustion gases. The kiln is charged with .solid fuelandcement-formingmaterial in the form of nodules or briquettes 'I I.

Intermediate the upper and lower ends of the shaftlZ a numberof-ou'tle'ts l2, distributed around the periphery and each having a.proportioning valvejl3, lead from the interior of the shaft 2 intomanifolds 14 disposed .on either side of the kiln and interconnected attheir upper ends to ,form a single escape conduit 15 having a controlvalvellidisposed in the conduit l5 above the point of interconnection.

Partway down from the top of the shaft a K number of openings 11communicate with the manifolds l4 and constitute inlets l8 each of whichhas a propor'tioning valve l9, whereby the manifolds M are placed incommunication with the 'interior of the upper part of the shaft 2.

Intermediate the outlets l2 and the inlets It further inlets around theperiphery of the furnace lead from the manifolds 14 into the interior ofthe shaft 2 each of which is provided with a proportioning valve 2 I.Partway 'up from the bottom of the shaft 2 two additional diametficallyopposed outlets 22 lead from the interior of the lower part of the shaftinto the manifolds M.

The escape conduit 15 communicates with a drying chamber 23 having anoutlet 24 into the chimney 1 0. A feeder conveyor 25 passes through thedrying chamber 23 from which the material is discharged through a chute26 into the hopper 1;

Above and adjacent to each of the inlets l8 and 20 and the outlets I2 athermo-couple 21 is inserted in the wall :of the kiln I. Thethermocouples 2] are electrically connected to a regulator 28 which inturn is electrically connected ,toeach of the proportioning valves I3,I9 and 2|. "The electrical connecting means between the "thermo-couplesand the regulator, and between the regulator and the proportioningvalves are indicated diagrammatically by dotted lines and may be carriedout by any known means.

The-cement kiln functions as follows:

Solid fuel and cement-forming material in the 'formiof modules orbriquettes ii is charged into the top of the kiln I and passes down theshaft ,2 :in counter-current to an ascending air blast. As the materialpasses down the shaft its temperature progressively increases until'the' material reaches a point at which combustion commences. This pointrepresents the boundary between the pre-heating zone A and thecombustion zone B. As the material passes down through the combustionzone B its temperature rises and falls until the material reaches asecond point at which combustion ceases, thereafter the materialprogressively cools until it reaches the bottom of the shaft where it isdischarged through the rotary grate into the discharge chute 4. Thissecond point represents the. boundary between the combustion zone 'B andthe cooling zone C.

Blast air is introduced into the shaft 2 at the bottom of the coolingzone C through the opening 6 in the top of the discharge chute 4 andthrough the rotary grate 3, the quantity of air supplied being usuallysuch as to ensure adequate combustion of the solid fuel. If, accordingto the invention, an additional amount of air is introduced into thebottom of the cooling zone, it follows that the material will bedischarged from the kiln at a considerably lower temperature, 'due tothe cooling effect of the excess air.

In order that only that amount of air required for adequate combustionof the :solid fuel shall therefore reach the combustion zone, aproportion of the blast air :so supplied to the cooling zone is laterremoved from the cooling zone by means provided for that purpose. .Asthe blast air ascends the shaft 2 a, proportion of the air escapes fromthe lower part of the cooling zone C through the outlets '22, into themanifolds l4, and eventually into the escape conduit Hi. This aircarries with it a quantity of heat abstracted from the material in thelower part of the cooling zone '0. As the remaining air ascends stillfurther it absorbs a further quantity of heat from the cooling zone C. Afurther proportion of the blast air can be removed from the upper partof the cooling zone C through the outlets [-2 into the manifolds Mthrough the "proportioning valves 1-3. The amount of air so removed iscontrolled by ther mo-couples 21 in conjunction with the thermoelectricregulator 28 which is connected to the proportioning valves 13. In thisway the boundary between the cooling zone C and-the combustion zone Bmay be maintained at a predetermined height or the whole zone orsections of it maybe adjusted upwards or downwards as desired. V

A proportionof the blast air removed from the "cooling zone may, ifdesired, be returned to the combustion zone B, through a part or throughall of the inlets 20, leading into the combustion zone in order toequal-ise the combustion around the periphery, the amount of air soreturned -being controlled'by "the thermocouples 21 in conjunction withthe regulator 28. A'further proportion of the blast air may be returnedto the heating zone A, thereby returning heat abstracted from the loweror cooling part to the heating or upper part of the system. This airenters the heating zone A through "the inlets l8 and the proportioningvalves '19 which are controlled in like manner as described above, by afurther pair of thermocouples 2! and the regulator 28.

The remaining portion of the blast air removed from the cooling zone,and which is at a substantially high temperature, may be allowed toescapeto atmosphere through the escape conduit 15 and control valve 16,or it may be used for heating or drying purposes outside the kiln. Inthe present case the remaining portion of hot blast air is conductedthrough the escape conduit l5 and the control valve I15 to the dryingchamber 23 from which it passes through the outlet 24 into the chimneyI0.

By virtue of this arrangement the nodules or briquettes may be pre-driedby passing them through the drying chamber on the feeding conveyor 25before discharging them through the chute 26 into the hopper I. In thisway therefore, a substantial amount of heat, which would otherwise bewasted is returned to the system, thereby reducing waste heat to aminimum and as a result considerably improving the operating efficiencyof the kiln.

The kiln may, for example, have a height of some 30 feet and an internalshaft diameter of some seven feet, and may be charged at the rate oftons per hour, with nodules or briquettes of the following composition:11.7% silica, 5.6% alumina, and iron oxide, 36.3% lime, and 45.3% solidfuel. The air blast may then be adjusted so that come 6000 cu. ft. 1: erminute passes directly upwards from the cooling zone C to the combustionzone B whilst up to a further 6000 cu. ft. per minute is diverted fromthe cooling zone C and further employed in the manner described.

Whilst specific figures of dimensions, compositions, quantities of airand rates of charging have been given, solely by way of example, itshould be understood that they in no way are binding and may be variedconsiderably depending on circumstances.

What I claim is:

1. A method of operating a vertical shaft furnace in which discretematerial comprising solid fuel is charged at the top of the shaft andpasses down said shaft in countercurrent to an ascending air blastintroduced at the bottom of said shaft to form within said shaft apreheating zone near the upper end, a cooling zone near the lower endand a combustion zone intermediate but adjacent said other two zones,comprising the steps of supplying said air in an amount in excess ofthat needed to obtain adequate combustion of said solid fuel in saidcombustion zone and removing from the periphery of the upper part ofsaid cooling zone that part of the ascending air blast introduced at thebottom of the shaft which is in excess of the amount needed forcombustion of the said solid fuel in said combustion zone so that agreater amount of air passes through the cooling zone than through thesaid combustion zone whereby the cooling of the material in the coolingzone i accelerated and a substantially uniform depth of the combustionzone is obtained.

2. A method of operating a vertical shaft cement kiln associated with adrying device for briquettes or nodules comprising cement formingmaterial and solid fuel comprising the steps of charging from saiddrying device briquettes or nodules into the top of said kiln,introducing into said kiln from the bottom thereof an ascending airblast to establish within said kiln a preheating zone near the upperend, a cooling zone near the lower end and a combustion zoneintermediate said other two zones, the amount of air introduced into thekiln being in an amount in excess of that needed for adequate combustionof said solid fuel in said combustion zone, adjusting the amount of airpassing through the combustion zone to the amount needed for adequatecombustion by removing part of the ascending air blast, before enteringthe combustion zone, from the periphery of the upper part of the coolingzone and supplying at least part of the air blast so removed to the saiddrying device and using it for predrying the nodules or briquettesbefore they are charged into the kiln.

3. In the method of operating a vertical shaft furnace in which discretematerial comprising solid fuel is charged at the top of the shaft andpasses down said shaft in countercurrent to an ascending air blastintroduced at the bottom of said shaft and in which a preheating zonenear the upper end, a cooling zone near the lower end and a combustionzone intermediate but adjacent said other two zones are formed, thesteps of supplying said air blast in an amount in excess of the airneeded to obtain adequate combustion of said solid fuel in saidcombustion zone, adjusting the amount of air passing through thecombustion zone to the amount needed for adequate combustion by removingfrom the periphery of the upper part of said cooling zone a part of theascending air blast, before entering the combustion zone, andintroducing at least part of the air blast removed from said coolingzone to said preheating zone through peripheral. inlets such that agreater amount of air passes through the cooling zone than through saidcombustion zone.

4. In a vertical shaft furnace of the kind in which charging means areprovided for supplying discrete material consisting at least in part ofsolid fuel to the upper end of the furnace and in which air supply meansare provided for supplying at the lower end of the furnace an ascendingair blast in excess of the amount of air needed for combustion of saidfuel, said furnace including a preheating zone, a combustion zone belowsaid preheating zone and an adjacent cooling zone below said combustionzone, outlet means for combustion gases at the upper end of the furnaceabove the preheating zone, discharge means for nongaseous combustionproducts at the lower end of the furnace below the cooling zone, atleast one adjustable outlet passage arranged peripherally at the upperend of said cooling zone for discharging an adjustable part of the blastof air from the periphery of the cooling zone adjacent the combustionzone, and at least one inlet passage arranged peripherally of saidpreheating zone and connected to and communicating with said outletpassage at the upper end of said cooling zone whereby said adjustablepart of the blast air is bypassed around and prevented from passingthrough said combustion zone.

5. In a vertical shaft cement kiln of the kind in which charging meansare provided for supplying nodules 0r briquettes of solid fuel andcement forming material from a drying chamber directly to the upper endof the kiln, air supply means for supplying at the lower end of the kilnan ascending air blast in excess of the air needed for adequatecombustion of said fuel, said kiln including a preheating zone, acombustion zone below said preheating zone and a cooling zone below saidcombustion zone, outlet means for combustion gases at the upper end ofthe kiln above the preheating zone, discharge means for the cement atthe lower end of the kiln below the cooling zone, and at least oneadjustable outlet passage arranged peripherally at the upper end of saidcooling zone for discharging an adjustable part of the blast of air fromthe periphery of said cooling zone adjacent the combustion zone, saidoutlet passage at the upper end of the cooling zone being connected toand communicating with said drying chamber to dry the nodules orbriquettes of solid fuel and cement forming material before beingcharged into the kiln.

6. In a vertical shaft cement kiln of the type comprising charging meansfor supplying nodules or briquettes containing cement forming material Iand solid fuel to the upper end of the kiln and air supply meansforsupplyingan ascending air blast through said kiln from the lower end of:the kiln to establish a preheating zone in the upper part of the kiln, acooling zone in the lower part of the kiln and a combustion zoneintermediate said preheating and cooling zones and directly adjacentthereto, outlet means for combustion gases at the upper end of the kilnabove said preheating zone and discharge means for the clinker at thelower endof the kiln, the provision of means for supplying said airblast in an amount in excess of the air needed for adequate combustionof said solid fuel in said combustion zone, of at least one adjustableoutlet passage arranged peripherally at the upper end of said coolingzone for discharging an adjustable part of the blast of air from theperiphery of the cooling zone adjacent thecombustion zone, whereby thecooling of the material in the cooling zone is accelerated and asubstantially uniform depth of the combustion zone. is obtained and ofinlet means arranged peripherally of said preheating zone and connectedto. said outlet passage, whereby said adjustable part FRANCIS PAULSOMOGYI.

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